On Tue, Jun 08, 2010 at 10:38:07AM +1000, Dave Chinner wrote: > From: Dave Chinner <dchinner@xxxxxxxxxx> > > sync can currently take a really long time if a concurrent writer is > extending a file. The problem is that the dirty pages on the address > space grow in the same direction as write_cache_pages scans, so if > the writer keeps ahead of writeback, the writeback will not > terminate until the writer stops adding dirty pages. > > For a data integrity sync, we only need to write the pages dirty at > the time we start the writeback, so we can stop scanning once we get > to the page that was at the end of the file at the time the scan > started. > > This will prevent operations like copying a large file preventing > sync from completing as it will not write back pages that were > dirtied after the sync was started. This does not impact the > existing integrity guarantees, as any dirty page (old or new) > within the EOF range at the start of the scan will still be > captured. > > This patch will not prevent sync from blocking on large writes into > holes. The writes don't have to be into holes to cause this starvation problem, do they? > That requires more complex intervention while this patch only > addresses the common append-case of this sync holdoff. Jan's tagging patch looks pretty good to me and isn't so complex. I think we should just take that. -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
